And he responded to him: "I am. Go and tell your lord that Elijah is here.
Other versions
King James Version
And he answered him, I am: go, tell thy lord, Behold, Elijah is here.English Standard Version
And he answered him, "It is I. Go, tell your lord, 'Behold, Elijah is here.'"New International Version
"Yes," he replied. "Go tell your master, 'Elijah is here.'"